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Full text of "John_Deere_Hyrostatic_Tractor_120"

SLIDE TEXT 
ST-120 



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CONSUMERS PRODUCTS 

120 
HYDROSTATIC TRACTOR 




•■^ 



SECTION 10 
GENERAL 1 



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120 HYDROSTATIC TRACTOR 

INTRODUCTION 

New for 1970 is the 120 Lawn and Garden 
Tractor. The 120 is a 12 HP Hydrosta- 
tic Drive Tractor. This tractor will 
fill the gap between the 112 and 140 
Tractors. 



The 120 has the general appearance of 
the 140 HI Tractor and should appeal to 
the homeowner. 

The following service program will cover 
the 120 Tractor. There are items which 
will be similar to the 140, however, the 
140 Tractor has a printed Service Manual 
available (SM 2086). The 120 Tractor 
will have a separate Service Manual (SM 
2090). 

SPECIFICATIONS: 





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Dimensions 

Wheel Base '^6 in. 

Over-all Length 67-1/2 in. 

Over- all Height 43 in. 

Over-all Width (Min) 38 in. 

(Max) 42-1/2 in. 

Wheel Tread (Center-to-Center) 
Front (GT-3, GT-5 

and GT-6) 31-1/4 in. 

Front (GT-4) 29-1/2 in. 

Rear (GT-3, GT-4 

and GT-6) 30-1/2 or 32-1/2 in. 



Tire Sizes 

GT-3, GT-5 and GT-6 

Front 16x6.50-8 2-ply 

GT-3 Rear 23x8.50-12 2-ply 

GT-4 Front 4.80/4.00-8 4-ply 

GT-4 and GT-6 

Rear 23x8.50-12 2-ply 

GT-5 Rear 23x10.50-12 2-ply 

Tire Inflation 
GT-3, GT-5 and 

GT-6 Front 6 to 16 psi 

GT-3 Rear 5 to 10 psi 

GT-4 Front 12 to 40 psi 

GT-4 and GT-6 

Rear 5 to 10 psi 

GT-5 Rear 5 to 10 psi 

Curb Weight 736 lbs . 



- 1 - 



SECTION 10 
GENERAL 2 



PREDELIVERY 

The 120 Tractor will be shipped assem- 
bled, less the hood and seat (colored 
tractors only) and rear tires on the 
GT-5 option. 

Assemble the tractor and attachments 
according to the PDI instructions in 
the Operator's Manual. Be sure to re- 
move the battery for activation. Bat- 
tery acid is not shipped with the trac- 
tor and is available from the parts de- 
pot. 



120 GEN 2 




******-k***-k**-k-k-k-ki,ifi,^ 



The free wheeling valve is open when 
the tractor is shipped from the factory. 
With the valve open the tractor can be 
moved without starting the engine. 

To close the free wheeling valve, turn 
the knob counterclockwise about 10 re- 
volutions. If the tractor will not 
move with the engine running be sure 
the free wheeling valve is closed. 



120 GEN 3 




Be sure the customer has his Operator's 
Manual at the time of delivery. 

Explain periodic maintenance checks. 

Instruct the customer of safe operation 
practice. 



120 GEN 4 




****i(**-k*it-k-/t 



********* 



- 2 - 



SECTION 20 
ENGINE 1 



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ENGINE SPECIFICATIONS 

ENGINE 

Manufacturer Kohler 

Model K301AS 

Cylinder One 

Cycle Four 

Bore and Stroke 3.38x3.25 in. 

Displacement 29.07 cu. in. 

Speeds Fast - (No load) 3800 rpm 

Speeds Idle - (No load) 1200 rpm 

Horsepower (Engine Manufacturers 

Rating) 12 (? 3600 rpm 

Valve Clearance (Intake) 

Cold 0.010 in. 

Valve Clearance (Exhaust) 

Cold 0.020 in. 

Crankcase Capacity 3 US pints 

Engine Crankcase 

Summer SAE 30 (AM 30730) 

Winter SAE 5W-20 (AM 30710) 



120 ENG 1 




There are three requirements for an en- 
gine to operate. They are air, fuel and 
spark. A deficiency of any one of tkese 
will cause trouble. 



Air be sure the air filter is ser- 
viced properly. Tap filter lightly to 
remove dirt. Never use compressed air 
or a liquid cleaner of any type to clean 
filter as these may damage air filter 
and result in damage to the engine. Re- 
place filter every 100 hours of service 
or sooner if it becomes extremely dirty. 

Fuel use only regular grade gasoline, 

never use a premium grade gasoline. Main- 
tain a clean fuel tank, line and strainer. 
Caution customer about the common prac- 
tice of contamination with gasoline. 
Nothing will interrupt operation faster 
than dirty or contaminated fuel. 

Spark maintain a clean spark plug. 

Proper spark plug gap is .025-inch. If 
the electrodes have burned short or have 
become pitted install a new spark plug 
of the proper size. (Notice not just 
any spark plug. ) 



■k -k * 



****************** 



- 3 - 



SECTION 20 
ENGINE 2 



The serial number plate for the engine 
contains several groups of numbers. The 
serial number of the engine is the num- 
ber which is immediately below the words 
serial number on the serial plate. This 
number is valuable to the factory and 
should appear on warranty claims and 
correspondence referring to engine pro- 
blems. 



120 ENG 2 




ENGINE REMOVAL 



120 ENG 3 



Remove the (4) bolts holding the hood 
cowls to tlie frame and remove the hood 
and grille components as an assembly. 

Disconnect the positive and negative 
battery cables at the engine. 



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Disconnect the wiring harness at the 
three prong connector and electro- 
magnetic clutch connection. Shut off 
fuel valve and remove gas line. Dis- 
connect throttle and choke control cables 
(Air filter and carburetor back plate 
removed for clarity.) 

Remove the two bolts holding the flex 
coupling to the drive shaft. Remove the 
(4) bolts connecting the engine to the 
frame and lift the engine up and out of 
the tractor. 

For assembly, reverse the removal proce- 
dure. 

The 120 Tractor will have its own Ser- 
vice Manual. Until the time you receive 
your Service Manual, you may refer to SM 
2086 140 Hydrostatic Tractor for most 
of the engine disassembly and reassembly 
procedures, trouble shooting and diag- 
nosis. 



120 ENG 4 




- 4 - 



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SECTION 20 
ENGINE 3 



NOTE: Insert throttle cable in the lower 
of the two holes on the adjusting screw lever. 
Raise the control lever to the fast position. 
To properly position throttle cable, hold 
the adj lis ting screw lever rearward against 
the stud while tightening the clip on the 
control cable. 



120 ENG 5 




********************* 



To adjust the governor, set the throttle 
cable as previously described. Start the 
engine and raise the control lever to the 
fast position. Turn the governor adjust- 
ing screw clockwise to decrease maximum 
rpm. Turn the governor adjusting screws 
counterclockwise to increase maximum rpm. 

Maximum rpm is 3800 no load and idle 
speed is 1200 rpm. Shown is a vibrating 
tachometer available from Tecumseh, 
(Part No. 670156, current price $3.95.) 
which will enable you to set the engine 
speed accurately. 



120 ENG 6 




******************** 



- 5 - 



SECTION 30 
FUEL SYSTEM 1 



SPECIFICATIONS: 

Fuel System 

Type of Fuel Regular Gasoline 

Filter In-line Strainer 

Fuel Tank Capacity .. 1.75 US Gallons 

Air Filter 

Type AM31400 Dry Filter 



ADJUSTING CARBURETOR 

Idle adjustment and high speed adjust- 
ment must be made at the same time as 
each affects the other. Adjust as fol- 
lows: 

1. Be sure choke lever is down 
(choke open) . Turn high speed 
mixture needle (A) clockwise 
until closed. Close finger 
tight only. Then open one- 
and-one half turns. 

2. Turn idle mixture screw (B) 
clockwise until closed. Close 
finger tight only. Then open 
two complete turns. 

3. Start engine and raise throttle 
lever on dash panel to "fast" 
position. Allow engine to warm- 
up. 

4. Turn high speed mixture needle 
(A) 1/8 turn each time, clockwise 
or counterclockwise until engine 
runs smoothly at full throttle. 
Keep needle position slightly on 
the rich side (open) when opera- 
ting tractor with power-driven 
equipment such as the mower or 
snow thrower . 



120 FS 1 




Move throttle lever to "slow" 
position and turn idle mixture 
screw (B) 1/8 turn each time, 
clockwise or counterclockwise 
until engine idles smoothly. 

Advance throttle lever quickly 
to check for uniform acceleration. 
If engine misses, gas-air mixture 
is too lean. Turn high speed mix- 
ture needle counterclockwise until 
positive acceleration can be ob- 
tained. 



- 6 - 



If excess exhaust smoke is noticed, mix- 
ture is too rich. Readjust idle mixture 
screw if necessary, until good balance 
is achieved and engine idles smoothly 
between 1200 and 1700 rpm. The idle stop 
screw (C) adjusts the speed at which the 
engine idles. This is factory-adjusted 
and will not normally require adjustment. 

Carburetor and fuel tank and lines ser- 
vice is shown quite well in SM 2086. 



SECTION 30 
FUEL SYSTEM 2 



* * * A 



***************** 



- 7 - 



SPECIFICATIONS: 

Electrical System 

Ground Negative 

Battery - JOHN DEERE AM 31186 

40 amp-hr. , 12-volt 
Starter Switch Ignition Key and 

Solenoid 

Ignition Battery 

Spark Plug gap 0.025 in. 

Breaker Point Gap 0.020 in. 

Voltage Regulator Fuse SEE 14 amp. 



SECTION 40 
ELECTRICAL SYSTEM 

1 



120 ELECT 1 




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The 120 Tractor has battery coil ignition. 
Shown is the wiring diagram of the 120. 

If problems are encountered with the 
cranking system, the ignition switch, 
solenoid and neutral start switches 
should be checked to determine if they 
are working properly. Test procedures 
are outlined in the 120 and 140 Service 
Manual. 



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TESTING BATTERY 

Checking Specific Gravity 

To determine whether the battery is ca- 
pable of meeting the requirements of the 
starting motor, it is necessary to du- 
plicate operating conditions by subject- 
ing the battery to a load test. To ob- 
tain a true test, the battery should be 
at least 75 percent charged. This can 
be determined by taking a hydrometer 
reading. 

The following table illustrates typical 
ranges of specific gravity (amount of 
unused sulfuric acid remaining in the 
solution) for a cell in various states 
of charge, with respect to its ability 
to crank the engine at 80° F. with ini- 
tial full-charge specific gravity at 
either 1.260 or 1.280. 



120 ELECT 2 




- 8 - 



SECTION 40 
ELECTRICAL SYSTEM 
2 



Specific Gravity 


Capacity 


1.260 to 1.280 


100% 


1.230 to 1.250 


75% 


1.200 to 1.220 


50% 


1.170 to 1.190 


25% 


1.140 to 1.160 


Very little 
Useful capacity 


1.110 to 1.130 


Discharged 



********************* 



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Checking Battery Voltage 

There are two methods of testing battery 
capacity. Battery electrolyte tempera- 
ture should be at or near 80 degrees 
Fahrenheit for these tests. 

Before making either of the two follow- 
ing tests, first check electrolyte level 
in battery. Add water if necessary. 
If water is added, be sure it is thor- 
oughly mixed with the underlying elec- 
trolyte by charging. Battery voltage 
should be 11.5 to 12.6 volts before 
testing. Refer to instructions supplied 
by test equipment manufacturer, when 
using high-rate equipment. 

Using the first method, crank the engine 
for 15 seconds with the starting motor 
and measure the battery voltage. If 
voltage is less than 9.6 volts at the 
end of 15 seconds replace battery. 



120 ELECT 3 




* * * * * 



**************** 



As a second method, use heavy load dis- 
charge test equipment. 

Discharge the battery according to the 
manufacturer's recommendations for test- 
ing. 

If after testing the battery voltage is 
less than 9.0 volts, the battery fails to 
meet the load test, indicating loss of 
capacity or internal short circuits. Any 
battery that passes the load test is a 
good battery and can be relied upon to 
fulfill the requirements of the starting 
motor under normal conditions. 



120 ELECT 4 




********************* 
- 9 - 



SECTION 40 
ELECTRICAL SYSTEM 
3 



Repairing Starter 

Repair to the starter is limited to the 
brushes, end cap, armature and starter 
drive assembly. Any of the parts can 
be replaced if found to be defective. 
Field coils in this starter are perma- 
nent magnets and no service is required 
or possible. Any serious defect in the 
magnets will require a complete starter 
replacement. 

Removing Starter 

Disconnect negative cable from battery. 

Disconnect solenoid-to-starter cable 
from starter terminal. 

Remove two mounting bolts holding 
starter to engine block. 



120 ELECT 5 



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A * A 



Starter Drive Service 

Remove starter drive by holding drive 
gear and turning 3/8-inch lock nut off 
armature shaft. After lock nut has 
been removed the three parts of the 
drive can be removed. 



120 ELECT 6 




****-k**-k-k-k*-k-k*****-k 



■k * 



Starter Service 



120 ELECT 7 



Remove the two thru bolts which hold 
the end caps to starter housing. Re- 
move 1/4 X 5/8-inch capscrew from rear 
brace. Tap rear brace downward to pro- 
vide room for removal of end cap. 

Remove the end cap carefully to avoid 
loosing brush springs which will pop 
out when end cap is removed. 



■^ 




- 10 - 



SECTION 40 
ELECTRICAL SYSTEM 
4 



Brush Service 

Replace brushes whenever they show any 
appreciable amount of wear. To replace 
input brush assembly, remove nuts and 
washers from terminal and pull out thru 
the inside of cap. The input brushes 
are to be placed into the insulated 
brush holders when assembling. 

The leads from the ground brushes are 
attached to the metal screws which se- 
cure the insulated brush holders to the 
end cap . 



A * * 



****************** 



The preparation of the starter end cap 
is the first step in the assembly of the 
starter. 

First place brush springs into brush 
holders, then in succession place a 
brush in its respective holder with the 
beveled side up. 

Compress brush springs and place U-shaped 
clips made of banding steel onto each 
brush. 

Wipe commutator clean with a dry cloth 
and lubricate armature shaft with a 
small amount of light grease. 

Place armature into end cap, and retove 
brush retaining clips. 



120 ELECT 8 




* * * * * 



**************** 



Place starter housing over armature 
while holding down pressure on the arma- 
ture. This prevents the brush springs 
from pushing armature up and away from 
end cap. If this occurs, re-load brushes 
into end cap and reassemble. 

Align housing to end cap using the index 
marks on cap and housing as a guide. 

NOTE: The starter housing has a mark 
and an indentation on the inside which 
must fit into the two indentures on the 
end cap . 



120 


ELECT 9 








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************* 

- 11 - 



SECTION 40 
ELECTRICAL SYSTEM 
5 



Place steel spacer washer onto armature 
shaft and insert armature shaft through 
drive end bearing of mounting bracket. 

Insert thru bolts and torque to 20 to 
25 lbs. 

Position rear brace and install 1/4 x 
5/8-inch capscrew and tighten firmly. 

Install starter drive gear on armature 
shaft, anti-drift spring, spring cup 
and lock nut. Torque lock nut to 45 to 
50-inch lbs. 



120 ELECT 10 




Install starter to engine, using the two 
shoulder bolts previously removed. At- 
tach solenoid to starter wire and tighten 
all bolts firmly. 

NOTE: A thin steel shim is used with 
some early model starters between mount- 
ing bracket and engine. Re-install shim 
whenever original mounting bracket is 
re-used. 



******-k*******it*itis**-)s 



- 12 - 



SECTION 40 
ELECTRICAL SYSTEM 
6 



IGNITION SYSTEM 

The battery ignition system differs from 
the magneto ignition in two ways. 

1, Current is supplied to the ignition 
coil from the battery rather than from 

a permanent magnet self-powered magneto. 

2. The ignition switch must be closed 
in the battery system for the current to 
flow through the coil. Magneto systems 
require an open circuit type switch. 

The function of any ignition system is 
the same, and that is to produce a hot 
spark at the plug at the right time for 
ignition of the fuel mixture. 

Here is how that battery ignition works: 

With the ignition switch closed, current 
flows from the battery to the primary 
windings of the coil, and through the 
closed breaker points to ground. 



120 ELECT 11 




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At the point when the piston is near 
top dead center on the compression stroke, 
the breaker points are opened by the cam 
and push rod. 

When the points are opened, the primary 
electric circuit is broken and the mag- 
netic field breaks down. 

With the collapse of the primary field, 
the magnetic lines of force cut across 
the conductor coil windings and a high 
voltage is induced in the secondary 
windings . 

A spark occurs at the spark plug, which 
is in the secondary circuit. The high 
voltage developed in the secondary coil 
causes the current to jump across the 
spark plug electrode gap, thus making a 
spark. 

The residual current in the primary 
winding is absorbed by the condenser. 
This eliminates arcing at the points 
and aids in producing a stronger spark 
at the spark plug. 



********************* 
- 13 - 



SECTION 40 
ELECTRICAL SYSTEM 
7 



IGNITION TESTING 

The ignition coil is either in a satis- 
factory condition or it is not. Coil 
failure occurs all at once, much as an 
electric light bulb. It does not degen- 
erate gradually. 

When coil failure is suspected, use an 
analyzer to test coil. The analyzer will 
also test the condenser and solenoid as 
well as checking voltage and amperage. 
See equipment manufacturers operators 
handbook for specifications for parti- 
cular unit being tested. 

Follow manufacturer's recommendations to 
test the following: 

1. Coil power test 

2. Coil high speed test 

3. Coil surface insulation test 

4. Coil continuity test 

5. Coil ground test 



120 ELECT 12 




****is*******-k-/t*****i(-k 



The condenser can be tested with an ohm- 
meter. To do this, remove the condenser 
lead from the breaker points, then con- 
nect tester leads between the condenser 
lead and a good ground on engine. At 
first, a low resistance should be indi- 
cated. However, this should very quickly 
rise to a high value. If low resistance 
is indicated continuously, then conden- 
ser is definitely faulty and must be re- 
placed. 

Condensers can be tested off the tractor 
on test units. Follow manufacturer's 
recommendations to make the following 
condenser tests: 



120 ELECT 13 




1. Capacity 

2. Leakage 

3. Short 

4. Series resistance 



********************* 



- 14 - 



SECTION 40 
ELECTRICAL SYSTEM 
8 



Remove, inspect and regap spark plug to 
0.025-inch every 100 hours. Bend only 
the outer electrode when setting gap. 

Do not sandblast, wire brush, scrape or 
otherwise service plug in poor condition 
— best results are obtained with a new 
plug. 

Use a spark plug wrench to remove old 
plug. Always use a new spark plug gas- 
ket when replacing plug. Tighten plug 
to 15 to 20 ft. lbs. torque. 

Good operating conditions are indicated 
if plug has light coating of gray or tan 
deposit. A dead white, blistered coating 
could indicate overheating. 

A black (carbon) coating may indicate an 
over-rich fuel mixture caused by clogged 
air cleaner or improper carburetor ad- 
j us tmen t . 



120 ELECT 14 




********************* 



TIMING ENGINE (STATIC TIMING METHOD) 

Remove breaker point cover. Remove spark 
plug lead to prevent unintentional start- 
ing. Rotate engine by hand in direction 
of normal rotation (clockwise when viewed 
from flywheel end). Points should just 
begin to break as the "S" mark appears 
in the center of the timing sight hole. 

Continue rotating engine until points 
reach maximum opening. Measure gap with 
feeler gauge — gap should be 0.020-inch 
when fully open. 

If necessary, loosen point gap adjusting 
screw and adjust gap to 0.020-inch. Maxi- 
mum gap setting can vary from 0.018 to 
0.022-inch, to achieve smoothest running. 
Securely tighten adjusting screw after 
timing. 



120 ELECT 15 




********************* 



- 15 - 



SECTION 40 
ELECTRICAL SYSTEM 
9 



TIMING ENGINE (WITH TIMING LIGHT) 

Several different types of timing lights 
are available. Follow manufacturer's 
instructions for type used. The follow- 
ing timing procedure can be used with 
most timing lights. 

Connect one timing light lead at the 
spark plug terminal. 

Connect second timing light lead to po- 
sitive side of battery — see timing light 
instructions for battery size, wiring, etc. 

Connect third timing light lead to ground. 

Rotate engine by hand until "S" mark is 
visible. Chalk "S" line for easy reading. 
The "S" mark indicates the spark position, 
which is 20 degrees before top dead center. 

Start engine. Run at 1200 to 1800 rpm. 
Aim timing light into sight hole. The 
light should flash just as "S" mark is 
centered in sight hole of blower housing. 

If timing is off, remove breaker point 
cover, loosen gap adjusting screw and 
shift breaker plate until "S" mark is 
exactly centered. Re tighten adjusting 
screw before replacing breaker point 
cover. 



120 ELECT 16 




**A*********Vt*** 



* * * * * 



CHARGING SYSTEM 

Alternator 

An alternator system supplies electri- 
cal energy to charge the 12-volt battery. 
The battery, in turn, furnishes energy 
for cranking, lights, and other acces- 
sories. 

The 10-ampere alternator features (1) 
a permanent magnetic ring bolted to the 
inside rim of the fly-wheel, (2) an al- 
ternator stator assembly bolted to the 
engine bearing plate and (3) a rectifier- 
regulator unit mounted externally on the 
tractor. 



120 ELECT 17 







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- 16 - 



SECTION 40 
ELECTRICAL SYSTEM 
10 



The magnetic ring Is composed of 12 per- 
manent magnets imbedded in a cast ring. 

These high strength magnets are arranged 
between pole pieces providing an equal 
number of north and south magnetic poles. 

The magnetic ring, bolted to the inside 
rim of the fly-wheel rotates around the 
stator. 

As the magnetic ring rotates about the sta- 
tor, an alternating current (AC) is gener- 
ated in the stator winding. This alternating 
current is routed to a rectifier-regulator 
where it is converted to direct current (DC). 
Direct current conversion is required as 
the battery will not accept alternating 
current because of its electrical polarity. 

With this system, the battery and alter- 
nator work hand-in-hand to supply the 
needs of the engine and accessories — 
each one being dependent upon the other. 

The a^ltemating c^urrent produced in the 
alternator is changed to d^irect c^urrent 
in the rectifier- regulator unit. M- 
rect c^urrent is necessary for charging 
the battery. 

This change is accomplished through the 
use of solid state electronic devices 
which are arranged to form a full-wave 
bridge rectifier. 

Regulation is also provided by electronic 
devices (Zener diodes) which "sense" the 
counter-voltage created by the battery 
to control or limit the charging rate. 
Since these devices generate heat in 
operation, the regulator is equipped 
with finned surfaces to provide a greater 
cooling surface. 

When the battery is in a low state of 
charge, the regulator permits a higher 
charge rate to the battery. When bat- 
tery is fully charged, the devices li- 
mit the charging rate. 



********************* 



- 17 - 



SECTION 40 
ELECTRICAL SYSTEM 
11 



CHARGE CIRCUIT TESTING 

When testing the charging system of the 
tractor, use the following sequence: 

It is Important to inspect for a blown 
SfE-lA fuse in the rectifier-regulator 
before proceeding to test the charging 
system. 

Replace fuse and inspect for original 
cause of system short or overload. 

Start engine. Remove 3-prong connector 
from rectifier-regulator unit. Insert 
leads from AC voltmeter into the two 
outer plug connections. Check voltage 
recorded with engine running at full 
speed (no load) . 

Alternator should supply 28 to 32 volts 
to the regulator. 

If no charge is being received by the 
battery (0 ammeter reading) and voltage 
is substantially below 28 volts. the 
stator is defective and should be re- 
placed. 

If no charge is being received by the 
battery (0 ammeter reading) and voltage 
is more than 25 to 28 volts, the stator 
is producing properly. Therefore, by 
process of elimination, the rectifier- 
regulator must be at fault. 



120 ELECT 18 




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****-k**ieit-kisi,-k 



******** 



DC AMPERES TEST 



To check amperage, battery must be in 
need of some charge value. If battery 
is partially discharged, proceed, if 
not, remove spark plug wire and crank 
engine 15 seconds to partially dis- 
charge battery. Install spark plug 
wire. 

Caution: Never start an engine through 
a test meter. 

Start the engine and install ammeter in a 
series between battery positive cable and 
positive battery post. 




18 - 



SECTION 40 
ELECTRICAL SYSTEM 
12 



Adjust polarity on meter. Ampere read- 
ing should be from 1 to 10 amps depend- 
ing on battery condition. If battery 
is partially discharged and no amps are 
available, and previous test proved the 
alternator to be functioning properly, 
the rectifier-regulator is defective. 

If DC voltage and amperage prove satis- 
factory, there is no reason to service 
the charging system if battery will not 
stay charged. The problem would be in 
the battery. 



********************* 



r^'. 



19 - 



SECTION 50 
POWER TRAIN 
1 



SPECIFICATIONS: 

Brakes 

Type .. Double-Acting, Pedal-Operated 
Parking Hand Lock to Foot Brake 

Transmission 

Manufacturer Sundstrand 

Model No. 15-15 Series 

Oil Reservoir Rear Axle Housing 

Capacity 5 US Quarts 

Lubricant JOHN DEERE Type 

303 Special-Purpose 
(R34690R) or 
Automatic Trans- 
mission - Fluid 
Type "A" 

Travel Speeds 

Forward 1/2 to 6-3/4 mph 

Reverse 1/2 to 3-3/4 mph 

DRIVESHAFT SERVICING 
Remove roll pins which attach drive 
shaft yokes to drive shaft. Remove 
capscrews that retain the rear yoke to 
flexible disk. Slide shaft forward and 
remove rear yoke. With the rear yoke 
removed it is possible to slip drive 
shaft out with ease. 



120 PT 1 



•v^ 




After the drive shaft has been removed 
the flex-coupling can be removed from 
the clutch cone by removing the two re- 
taining capscrews. 

To service the clutch assembly it is 
suggested that the engine and clutch 
assembly be removed as an assembly. 
This provides for a better inspection 
and repair procedure. 

Remove engine and clutch assembly by 
removing engine mounting bolts, dis- 
connecting fuel and electrical wiring 
and finally unbolting flex-coupling 
from clutch cone. Attach hoist and lift 
complete engine assembly forward and up. 

Remove clutch assembly from engine by 
removing the four attaching capscrews. 
Disassemble and inspect internal components, 



********************* 



20 



SECTION 50 
POWER TRAIN 
2 



/-"N 



INTRODUCTION TO HYDROSTATIC DRIVES 

The hydrostatic drive is a fluid drive 
which uses fluid under pressure to 
transmit engine power to the drive 
wheels of the tractor. 

Mechanical power from the engine is 
converted to hydraulic power by a hydro- 
static transmission. This power is then 
converted back to mechanical power 
for the drive wheels. 

The hydrostatic drive can function as 
both a clutch and transmission. The 
final gear train can then be simplified, 
with the hydrostatic unit supplying in- 
finite speed and torque ranges as well 
as reverse speeds. 

Only three factors control the operation 
of a hydrostatic drive: 

Rate of oil flow — gives the speed 

Direction of oil flow — gives the 
direction 

Pressure of oil — gives the torque 

Control of these three factors is in- 
finite, giving endless selections of 
speed and torque in a hydrostatic drive. 



120 PT 2 



DRiVE SHAFT 



HYDROS rMlCi'" 



:DtfFEft6HTIAL 



********************* 



Hydrostatic transmissions use oil at 
high pressures but relatively low flow. 
Basically, energy is transferred by the 
oil itself in a continuous circuit be- 
tween the pump and motor as shown. 
While the oils does flow through the 
lines, it is still considered as being 
static (Stationary.) 



120 PT 3 



Hi-OROOl'NAUie 




HYDROSTATIC 



' V 



Fig, 2 — Basic Types Of Hydrauiic Transmissions 



********************** 



- 21 - 



SECTION 50 
POWER TRAIN 
3 



EXAMPLE: 

Two cylinders, each containing a piston, 
are connected by a line. The cylinders 
and the line are filled with oil. 

When a force is applied to the left 
piston as shown, that piston moves against 
the oil. The oil will not compress, so 
it acts as a solid and forces out the 
right piston. 

In a hydrostatic drive, several pistons 
are used to transmit power — one group 
in the pump sending power to another 
group in the motor. 



120 PT 4 




The pistons are in a cylinder block and 
revolve around a shaft. The pistons 
also move in and out of the block para- 
llel to the shaft. 



********************* 



Shown is one piston from the pump and 
one from the motor. To provide a pump- 
ing action for the pistons, a plate 
called a swashplate is located in both 
the pump and motor. The pistons ride 
against the swashplates. 

The angle of the swashplates can be 
varied so that the volume flow of the 
oil pumped by the pistons can be changed, 
Adjusting the swashplate affects flows 
and speeds . 



120 PT 5 



PUMP 
PISTON 



H ICZ 



CONNECTiNG 




'"is- 6 Two Connected Cylinders Wiih Swashplates 



********************* 



-^ 



- 22 - 



SECTION 50 
POWER TRAIN 
4 



r~>. 



A pump or motor with a movable swash- 
plate is called a variable-displacement 
unit. A pump or motor with a fixed 
swashplate is called a fixed displace- 
ment unit. 

As you have already learned, pumps and 
motors can have a fixed displacement 
or variable displacement. 

Four pump-motor combinations are possible: 

1) Fixed displacement pump driving a 
fixed displacement motor. 

2) Variable displacement pump driving a 
fixed displacement motor. 

3) Fixed displacement pump driving a 
variable displacement motor. 

4) Variable displacement pump driving a 
variable displacement motor. 



120 FT 6 




********************* 



OPERATION OF HYIHIOSTATIC 



120 PT 7 



Shown is a variable displacement pump 
driving a fixed displacement motor as 
is used in the 120 Tractor. 

As the pump pistons rotate, they move 
across the sloping face of the swash- 
plate, sliding in and out of their cyl- 
inder bores to pump oil in and out. 
The more the pump swashplate is tilted, 
the more oil it pumps with each piston 
stroke and the faster it drives the 
motor. 



The motor swashplate is at a fixed angle 
so that the stroke of its pistons are 
always the same. Thus its speed of 
rotation cannot be changed except as it 
is driven faster or slower by the pump 
oil. 

The point to remember now is that a 
given volume of oil forced out of the 
pump at a given pressure will cause the 
motor to tutn at a given speed.- More 
oil will increase the motor speed. Less 
oil will slow it down. 



- 23 - 



SECTION 50 
POWER TRAIN 
5 



The pump is driven by the tractor engine 
and so Is linked to the speed set by the 
operator. It pumps a stream of high- 
pressure oil to the motor. 

Since the motor is linked to the drive 
wheels of the tractor, it gives the 
tractor its travel speed. 

Since the pump flow is variable the 
output speed is variable. At any given 
pressure, output torque is constant. 



v^ 



********************* 



The pump-motor combination is the heart 
of the hydrostatic drive, although the 
complete hydraulic system also includes 
a reservoir to supply the oil, a filter 
to remove dirt, and a cooler to remove 
excess heat from the oil. 

Basically the pump and motor are joined 
in a closed hydraulic loop; the lines 
of the motor are joined directly to the 
pump. A charge pump supplies cooling 
and makeup oil for closed loop as well 
as implement oil. 



120 PT 8 




Fig. 9 — Pump-Mo'or Form A CloseU HydrauMc Loop 



********************* 



REVERSING IN VARIABLE PUMP CIRCUITS 

The direction of the motor output shaft 
rotation can be reversed by shifting the 
pump swashplate over center . 

NOTE: Pump input shaft always rotates one 
direction. 

In neutral, the swashplate is vertical 
and no oil is pumped. 

In forward, the swashplate is tilted and 
oil is pumped as shown at the top. 

In reverse, the swashplate is tilted the 
opposite way and the unit pumps oil in 
the opposite direction. 



120 PT 9 




^^ 



- 24 - 



SECTION 50 
POWER TRAIN 
6 



r^ 



CIRCUIT DIAGRAM 

Shown is the circuit diagram of the hy- 
drostatic used in the 120 Tractor. 

In order to keep the closed loop circuit 
full of oil a gerotor-type charge pump 
is used. 

Oil is supplied by the charge pump to 
the low pressure side of the circuit 
through one of the check valves. 

The high pressure oil on the high pres- 
sure side holds one check valve closed. 
The charge pressure oil on the other 
side is allowed to enter the low pressure 
side of the circuit, through the check 
valve, as needed. 

A pressure of 75 to 110 PSI is maintained 
by the charge relief valve. This valve 
also allows excess oil not needed by the 
closed loop to pass into the hydraulic 
lift circuit. The oil then continues 
through the lines to the open center 
valve and returns at low pressure through 
the pump case to the reservoir. 

The hydraulic lift circuit is protected 
from oil pressure damage by the imple- 
ment relief valve. Whenever pressure 
in the implement circuit exceeds approxi- 
mately 500 PSI, the valve opens, allowing 
oil to by-pass the implement circuit and 
flow into the case drain. 

The hydraulic system has controlled in- 
ternal oil flow, which lubricates cer- 
tain critical areas in the unit. 

Again, remember the charge pump supplies 
cooling and makeup oil as well as imple- 
ment oil. 



120 PT 10 






********************* 



- 25 - 



SECTION 50 
POWER TRAIN 
7 



HYDROSTATIC REMOVAL 

Remove the fender deck assembly by re- 
moving the (2) bolts in the front, (one 
on each side) and remove the nuts on the 
rear two rubber mounts . 

Remove the knobs on the mower depth stop, 
free wheeling control and park brake con- 
trol. 

NOTE: If tractor is equipped with lights, 
disconnect the taillight wires. 



120 PT 11 




Remove the shield covering the hydro- 
static unit and the two oil lines (top 
front) leading to the implement circuit. 

Remove the nut holding the speed control 
rod to the hydrostatic cam. 

Drive the roll pin out of the driveshaft- 
inputshaft coupling or disconnect the 
two bolts holding the yoke to the belt 
coupling. 



120 PT 12 




********************* 



Drive out roll pin holding fan on the 
rear of the hydrostatic and remove fan 
and fan guard. 



120 PT 13 




********************* 



Remove the bolts holding the transmission 
shield. Remove the rear transmission 
supports. Remove the tension spring on 
the hydraulic control lever. 



120 PT 14 



- 26 - 




SECTION 50 
POWER TRAIN 
8 



^-^ 



Block the tractor frame up to support 
tractor. Remove the (4) bolts holding 
the hitch plate to the frame. Discon- 
nect the brake connection. 



120 PT 15 




********************* 



Roll the transmission and differential 
assembly away from the tractor. Discon- 
nect the large oil cooling line and drain 
the oil. Remove the (4) bolts holding 
the transmission to the axle assembly. 

The hydrostatic is now ready for internal 
service. 



120 PT 16 














If'-' ■' 


jtflH^ 




iM'^ 


^hH^h 




V 


jiMM 




*' ^ nB£_ 


liuipHliH 




HnSS£^^ 





********************* 



Disassemble the hydrostatic as follows: 

TESTING AND DISASSEMBLY 

When experiencing problems with the trac- 
tor operation, always check the manual 
linkages before determining an internal 
hydrostatic component is causing the trouble. 

Charge Pump Relief Valve: 

The charge pump relief valve may be ser- 
viced without removing the transmission. 

Correct charge pressure is 75-110 PSI. 
This may be checked by tapping into the 
center section and connecting a pressure gauge, 
Be sure the hydrostatic is in neutral for 
this test. 

If replacing the charge relief valve as- 
sembly, you notice shims on the old as- 
setably, check the charge pressure after 
the new assembly has been installed. Due 
to tollerences in the machined parts in the 
center section, it may be necessary to add 
shims to get the proper pressure reading. 



120 PT 17 




- 27 - 



SECTION 50 
POWER TRAIN 
9 



Remove the charge relief valve plug, spring 
and cone from the center section of the 
housing. 

Wash and dry the components. Check the 
spring for pitting or rust. Check the 
cone for wear or damage. Check the seat 
in the center section of the housing for 
nicks, dirt or scratches. 

Install the relief valve in the center 
section as shown. Install a new 0-ring 
when reassembling. Torque plug 15-17 ft. 
lbs. 



120 PT 18 




Symptoms of defective charge relief 
valve assembly: 

1, Won' t move, 

2, Erratic or jerky, 

3, Lack of implement control. 



**********A**vi:A**A 



* * * 



Charge Pump Service: 



Caution: Thoroughly clean and deburr 
all shafts and housing before disassem- 
bling transmission. 

Remove the two hexs crews holding the 
charge pump to the center section hous- 
ing. Carefully remove the pump housing 
as the rotor assembly may stick to the 
housing. Do not drop the assembly. Re- 
move the rotor assembly if it did not 
come off with the housing. 

Note the method of retaining' the rotor 
gear with the rotor pin. 

The charge pump housing has a seal and 
0-ring, which are replaceable. 

Thoroughly libricate all parts with 
hydraulic oil before assembling (JD303) , 



120 PT 19 




!M 



***************vt**A** 



- 28 - 



SECTION 50 
POWER TRAIN 
10 



r^. 



r^ 



Reassemble rotor gear to pump shaft and 
secure with rotor pin. Install roller 
in the charge pump housing. Install hous- 
ing with flat edge to the charge relief 
valve side. The charge pump assembly 
is serviced as an assembly only. Torque 
the pump housing cap screws 50-55 ft. lbs. 

Symptoms of Defective Charge Pump: 

1. Erratic operation. 

2. Lack of operation. 

3 . Won ' t move . 

4. Lack of implement pressure. 



120 PT 20 




********************* 



Implement Relief Valve: 

Remove implement relief valve plug, spring 
and cone from the center section of the 
housing. Wash and dry the components. 
Check the spring for pitting or rust. 
Check the cone for wear or damage. Check 
the seat in the center section of the 
housing for nicks, dirt or scratches. 

Replace the relief valve in the center 
section as shown. Torque 15-17 ft. lbs. 

Symptom of defective implement relief 
valve could be lack of implement pressure, 
however, the charge pump relief valve or 
charge pump may be causing the problem. 

Implement pressure may be checked by 
attaching a gauge to the front outlets. 
Proper pressure is 500-550 PSI. 

NOTE: If shims were on the old valve, 
it may be necessary to check pressure 
and add shims to the new relief valve to 
arrive at the proper implement pressure. 



120 PT 21 




********************* 



- 29 - 



CHECK VALVES 

Again, it is not necessary to remove the 
transmission from the tractor to service 
the check valve. 

A quick external check of the check valves 
would be to push the pins in the center 
of the plugs down (with the engine running) 
and observe to see if they rise rapidly. 
It may still be necessary to remove the 
valves to be sure of their condition. 



SECTION 50 
POWER TRAIN 
11 



120 FT 22 




V_y 



**-k***-k-kit-k*-k**-k***i(AA 



Remove the check valve from the center 
housing. Wash valves in clean solvent 
and air dry. These valves are completely 
interchangeable. 

Check valves for dirt, corrosion and free 
plunger movement. 

The valves are serviced as an assembly 
only. Replace the valve if in doubtful 
condition. Always replace the 0-ring 
and back-up washer when reassembling 
check valves. These parts are serviced 
separately from the check valves. 

Lubricate all parts with hydraulic fluid 
and reinstall in center housing section. 

Symptoms: 

1. Won't move one direction or 
other. 

2. Erratic (maybe). 



120 PT 23 




***■!(*********■/(*■/!***** 



HYDROSTATIC DISASSEMBLY 

Be sure the outside surfaces of the 
transmission have been thoroughly cleaned. 
Place the transmission assembly in the 
holding fixture. 

Remove the charge pump assembly. Remove 
the oil filter. The oil filter union is 
to be 1/2-inch from the filter mounting 
surface. 



Ti^D n M 







- 30 - 



SECTION 50 
POWER TRAIN 
12 



r~^ 



Remove the cap screws securing the cen- 
ter section housing to the transmission 
housing. Torque bolts 33-37 ft. lbs. on 
reassembly. 

Lift the center section housing from the 
transmission housing. 

IMPORTANT: The valve plates may stick 
to the center section housing surface. 
Be extremely careful not to drop them. 



********************* 



Remove the pump and motor valve plates 
(if not removed with center section) 
noting the location of each plate. The 
valve plate with two notches is used on 
the pump assembly and the plate with 
four notches on the motor assembly. 

Thoroughly clean the valve plate and 
blow dry with compressed air. 

Inspect the valve plate for scratches, 
excessive wear or erosion. A worn or 
scored valve plate reduces pump effi- 
ciency. 

NOTE: To check the plate for wear, run 
your finger nail or a sharp pencil across 
the face of the plate. If wear is felt, 
replace the plate. 



120 PT 25 




********************* 



Inspect the pin slot and grooves of the 
valve plate. Clean out any foreign mat- 
ter and deburr the surface as necessary. 



JZQ,.E,TJ6 




********************* 



- 31 - 



SECTION 50 
POWER TRAIN 
13 



The center section needle bearings are 
replaceable. 

The new center section needle bearings 
must be installed so that they extend 
. 100-inch above the machined surface of 
the center section. The bearings "pilot" 
the valve plates when the unit is re- 
assembled. 

Then ends of the bearings with the print- 
ing go to the outside. 

************* 

Tip the transmission housing upside down 
holding the pump and motor cylinder 
block assemblies so they do not fall out. 
Holding the housing and one cylinder 
block assembly, remove the other cylin- 
der assembly. Then, remove the remaining 
cylinder block assembly. Do not let the 
piston fall out and get damaged. Do not 
mix the motor and pump pistons. 



************** 



120 PT 2 7 




120 PT 2 




Remove the pistons from the slipper re- 
tainer. Thoroughly clean the pistons 
and blow dry with compressed air. Be 
certain center oil passage is open. 



T2n PT ?Q 



************* 




- 32 - 



r^ 



Carefully inspect each piston for scor- 
ing, wear or scratches. 

Check the slippers for severe scratches or 
embedded material. Slippers may be lapped, 
but do not remove more than .005 inch. 
All slippers must be within .002 inch 
thickness of each other. 

Replace any pistons that are badly worn 
or scored. 

Inspect the slipper retainer for damage. 
A slight wear pattern where the slippers 
ride is normal. Replace if wear is ex- 
cessive. 



SECTION 50 
POWER TRAIN 
14 



120 PT 30 













********************* 



To disassemble the cylinder block it is 
necessary to compress the spring to re- 
move the retaining ring. 

A long bolt can be used with washers on 
each end to compress spring. 

CAUTION: Do not over tighten bolt as this 
will damage the spring retainer. 

Remove the retaining ring. 



120 PT 31 




********************* 



Carefully remove the bolt releasing the 
spring pressure. Remove the spring re- 
tainer, spring and spring washer. 

Thoroughly clean all parts and blow dry 
with compressed air. 

Check the spring against specifications. 
The spring in the piston block holds 
pressure against the valve plate. 

Check the cylinder block valve face for 
damage and the piston bushings for ex- 
cessive wear. Any linear scratches 
along the length of the bore will re- 
duce efficiency. Check piston fit in 
the bushings. 

Compress the spring, using the method 
explained above. Install the retaining 
ring. Release the spring pressure. 



120 PT 32 









1 

1 


to. 


^Oq 






m 



********************* 
- 33 - 



SECTION 50 
POWER TRAIN 
15 



Remove the cap screws securing the motor 
swash plate. 

Torque screws 60-70-inch lbs. on reas- 
sembly. 



120 PT 33 




Remove the transmission motor shaft and 
swash plate from the housing. 



120 PT 34 




The motor shaft bearing is to extend 
.18-inch from the housing. 



********************* 

120 PT 35 



********************* 



J 




- 34 - 



SECTION 50 
POWER TRAIN 
16 



r^ 



O 



Remove the trunnion shaft assemblies 
from the hydraulic pump swash plate by 
driving on the spring pins. The pins 
will bottom against the trunnion and 
will be centered in the trunnion shaft. 




********************* 



Remove the thrust plate and the swash 
plate from the pump section. 

Be sure to install the pump swash plate 
with the thin pad toward the top of the 
transmission housing. 

Inspect the thrust plate (for the pump 
swash plate) for wear, embedded material, 
or scoring. 

Inspect all the bearings and replace as 
necessary. 



120 PT 37 




********************* 



The trunnion bearings are to be installed 
flush or .005-inch below the inside sur- 
face of the housing. 



120 PT 38 




•:k:k'k'k':k'k-k-k-kii-k-k-k-k-:k-k:ki<:ki<:k 



- 35 - 



Pump shaft and trunnion shaft seals are 
to be flush or .005-Inch below the out- 
side surface of the housing. 

The seals may be replaced without dis- 
assembling the hydrostatic. 



SECTION 50 
POWER TRAIN 
17 



120 PT 39 




w^ 



****************;V**** 



REASSEMBLY 

Reassembly is basically the reverse of 
disassembly however, particular attention 
should be given the following: 

Thoroughly lubricate all parts in clean 
hydraulic oil. 

Pipe plugs or implement circuit fittings 
in the center section housing showing 
leakage must be removed, doped (teflon 
tape on the threads is ideal) and rein- 
stalled. 



120 PT 40 




v^ 



Use all new 0- rings , seals and gaskets. 

Be sure the thin pad of the pump swash 
plate is toward the top of the trans- 
mission housing. Seat the spring pins 
only flush with the trunnion as shown. 



****-ki<****-k*-k*isi:it**^it 



Be careful not to drop piston assemblies 
upon reassembly. Hold the unit as shown. 



120 PT 41 












« 








^ 


4 


-^"^ 


h 




^^y''*^ j^^^^B 




■ 


L 




^^■H 




} 


^k 




l^^^jhB 


M 


L 


W 


1 

:iM 



*A*A*************^^^^ 



- 36 - 



SECTION 50 
POWER TRAIN 
18 



Be sure the notches of the valve plates 
are in place over the studs in the center 
section. Grease the plates lightly to 
hold them during reassembly. 



120 PT 42 




************ 
Hold the unit on its side as shown for 
assembly. Be careful valve plates do 
not slip out of place. 

The springs in the cylinder blocks will 
hold the case and center section apart 
about 1/4 to 1/2 inch. This distance 
can be compressed by hand to be sure 
pieces are fitting properly. Replace 
the bolts holding the two sections to- 
gether. 



***** 

120 PT 



* * * 

43 




BRAKE SERVICE 



********************* 

120 PT 44 



Brake service may be performed without 
removing differential from the tractor. 

The wheel and hub being removed must be 
blocked up 6 to 8 inches to keep the 
oil from running out the axle tube. 

Remove the right rear wheel and bolt 
from the center of the hub. Replace the 
bolt in the hub without the flat washer. 

Use the puller as shown to remove the 
brake drum from the axle. 




********** 

With the drum removed, disconnect the 
(4) springs holding the brake shoes in 
place. Be careful not to cut the spring 
during removal and replacement. 



*********** 
120 PT 45 



- 37 - 




SECTION 50 
POWER TRAIN 
19 



If it was necessary to remove the (4) 
bolts holding back plate to seal retainer, 
it will be necessary to use a tool such 
as the one shox>m to center the retainer 
and seal with the axle shaft to get a 
good seal seat. The seal seats on the 
axle hub and brake drum surface. 

The tool is made from a piece of tubing 
with an outside diameter of 1.500 and 
an inside diameter of 1.130. The tool 
is also available from Service Tools, 
Inc., 1901 Indiana Avenue, Chicago, Illi- 
nois 60610 Part number JDST-9. 



120 PT 46 




Inspect the brake shoes for wear, dirt 
or oil contamination. If oil seal has 
been leaking, it may be necessary to re- 
place the shoes due to oil contamination. 

Install the shoes and (4) retaining 
springs. Be sure that the brake shoes 
fit into the rubber retainer on each end. 



****A*A**AA*******A*5!: 



Install the brake drum using a 7/16"x3" 
or longer NF bolt to draw axle shaft and 
brake drum together. 

Install the nut about half way up the 
bolt. Place a large flat washer over 
the bolt and turn the bolt into the axle 
shaft. 

Hold the head of the bolt and draw axle 
and drum together as shown by turning the 
nut. 

Do not try to drive the drum on the axle 
as this will push the bearing off the 
axle. The bearing has no snap ring or 
retainer ring. The bearing is a press 
fit on the axle. 

Make sure that the brake drum is not 
catching on the brake shoe during in- 
stallation. 



120 PT 47 




^y 



- 38 - 



Remove the bolt used to install the drum 
and reinstall the bolt and washer, which 
was originally removed from assembly. 
Torque the bolt 30 to 40 ft. lbs. 



SECTION 50 
POWER TRAIN 
20 



A*****A*:(cAA********** 



AXLE SHAFT, SEAL OR BEARING SERVICE 

Remove the rear wheel, axle hub or brake 
drum as was explained in the brake ser- 
vice section. It is not necessary to 
remove the differential from the tractor. 

Remove the (4) bolts holding the oil seal 
and retainer plate on the axle tube. No- 
tice the position of the retainer plate 
as it is removed. The rounded surface of 
the retainer plate goes to the outside 
next to the seal. 



120 PT 48 




********************* 



Pull the axle shaft out of the extension 
tube. 

Note the 0-ring on the shaft. If the 
0-ring is removed from the shaft, it will 
be necessary to install a new 0-ring. 
This 0-ring seats against the wheel hub. 




********************* 



The bearing on the axle shaft can be re- 
placed by pressing it off the shaft as 
shown. 

When installing the new bearing, be sure 
to press on the inner race only. Seat 
the bearing tight against the shoulder. 
Be sure to install a new 0-ring on the 
axle shaft. 

The cup may come loose from the bearing. 
If this occurs, clean the bearing and cup 
and reinstall in the axle tube. 



120 PT 50 




********************* 



- 39 - 



SECTION 50 
POWER TRAIN 
21 



Slide the axle shaft in the extension 
tube. Install the gasket, the retainer 
plate (rounded side out) , a gasket and 
the oil seal. Secure loosely with the 
(4) bolts. 

Use the seal tool (as explained in the 
brake service section) to center the oil 
seal with the axle shaft. This is im- 
portant, because if the seal is not cen- 
tered, it will leak oil. 

Tighten the (4) nuts 15-30 ft. lbs. The 
torque is important as it clamps the 
bearing in position. 



120 PT 46 




Install the hub back on the shaft. Use 
the 7/16" NF bolt as explained in the 
brake section to reinstall the hub on 
the shaft. 

Do not hammer hub on the shaft as it is 
possible to drive the bearing off the 
axle shaft. 

Torque the center bolt 30 to 40 ft. lbs. 
Do not reuse the bolt if it has lost its 
locking feature . 



********************* 



DIFFERENTIAL REMOVAL 

The differential assembly may be removed 
in the same manner as explained for hy- 
drostatic removal. 

After rolling the transmission and dif- 
ferential assembly away from the tractor, 
remove the hydrostatic and the wheels. 
Remove the hitch plate and drain the 
oil out of the axle. 



120 PT 16 




********************* 



- 40 - 



SECTION 50 
POWER TRAIN 
22 



r^ 



r> 



DIFFERENTIAL DISASSEMBLY 

With the differential assembly removed 
from the tractor, remove the hubs and 
axle shafts as previously described. 

Note: The axle shafts must be removed 
to be able to disassemble axle housing. 

Remove the (8) screws that hold the 
front housing to the rear housing. (The 
rear housing is the half with the hitch 
plate welded on.) There are two dowel 
pins connecting the case halves. Do 
not move or remove these dowels. 



120 PT 52 




****5V5': ;>;****** >'<******* 



With the front housing removed, look for 
the identification mark on the bearing 
caps and the case housing. The bearing 
caps are matched. Do not interchange 
them. Some early models did not have 
match marks and it is necessary to mark 
the caps for reassembly as shown. Also, 
note the position of the differential 
case in the bearing cradles. The long 
side of the differential assembly 
goes toward the side cover plate. 

Remove the (4) bolts that hold the bear- 
ing caps in place. Lift the differential 
assembly from the bearing cradles . If 
the differential sticks in the cradle, 
use two pieces of wood or hammer handles 
to pry the unit out. 

Do not interchange the bearing races. 



120 PT 53 




:k'k:kii-k:k:k'ki<iiii'f::k-J<-k-k'^:k-k-k'k 



Disassemble the differential assembly 
by driving out the roll pin as shown. 



120 PT 54 




**************** 

- 41 - 



* * * * 



SECTION 50 
POWER TRAIN 
23 



With the roll pin removed, use a punch 
to drive the pinion shaft out of the 
case. Be careful not to hit the ring 
gear while removing the roll pin or pin- 
ion shaft. 



120 PT 55 




*-k-k****-k-k*i<*-k-k-k 



***>!:* 



Rotate the pinion gears as shown to re- 
move them from the case. Remove the 
differential drive gears. 

If the pinion gears do not remove easily, 
use an axle shaft to turn the gears out. 



120 PT 56 




********************* 



The ring gear may be replaced by removing 
the (10) bolts holding it in place. Use 
a block of wood to knock the old gear off 
the case to prevent damage to the hous- 
ing. Clean the housing surface and in- 
stall the new ring gear and torque the 
bolts 45-60 ft. lbs. in a crisscross 
pattern. This will provide a uniform 
seat of the gear. 



120 PT 57 




********************* 



- 42 - 



SECTION 50 
POWER TRAIN 
24 



Install the thrust washers on the dif- 
ferential drive gear hubs. Grease the 
hubs and washers well and insert the 
gears into the differential case as 
shown. 





120 PT 58 








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Grease the pinion gear and thrust washer. 
Align the pinion gears and washer di- 
rectly opposite each other. Roll pin- 
ion gears in place by turning the dif- 
ferential drive gears until the holes 
line up. Be sure holes are directly 
across from each other on installation. 

Use a punch to be sure washer and pinion 
gears are lined up with the differential 
case. 



120 PT 59 




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Install the pinion shaft into case and 
pinions, being careful to line up roll 
pin hole in shaft and differential case. 

Drive roll pin into case and shaft from 

the long side of the case. Stake the 

roll pin in place. Be careful not to hit 

the ring gear with the hammer or punch. 

A noisy differential can be caused by hitting 

the ring gear with a hammer. 



120 PT 60 




********************* 



- 43 - 



SECTION 50 
POWER TRAIN 
25 



The differential bearings are replace- 
able. Remove them with a puller as shown. 
Note there are two grooves in the case 
to facilitate pulling. 

Note the shims under the bearings. These 
shims provide the backlash adjustment on 
the differential. The puller may mark 
the shims , 

If only one bearing is to be replaced 
use the same shims that are under the 
old bearing. 

If both bearings are to be removed, do 
not interchange the shims from side to 
side. 

If new bearings are being installed on 
a new case, start with .020 shim on 
each side. 



120 PT 61 




********************* 



Install the new bearing by pressing on 
the inner race only. Turn the shims un- 
der the bearing so the edge that was 
marked by the puller is in alignment with 
the notches in the housing. Seat bearing 
firmly . 



120 PT 62 




********************* 



To remove the spur gear, remove the 
side cover plate. 



120 PT 63 




********************* 



- 44 - 



SECTION 50 
POWER TRAIN 
26 



To remove the pinion assembly, drive a 
small punch into the cover of the welch 
plug about 3/8" from the edge. Pry the 
cap from the housing. 



120 PT 64 




********************* 



Remove the snap ring and spacer from 
the pinion shaft. 



120 PT 6 5 




********************* 



Rest the housing on a block of wood on 
the press bed so as not to damage the 
bearing cradle. Press the pinion out 
of the housing as shown. Place a screw- 
driver tip or about 1/8" material under 
the edge of the spur gear during removal 
of pinion shaft. This will eliminate the 
spur gear getting in a bind. 



120 PT 66 




********************* 



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- 45 - 



SECTION 50 
POWER TRAIN 
27 



This is the complete pinion and spur 
gear assembly. 

The bearing may be removed from the 
pinion shaft using an adjustable press 
plate and a hydraulic press. 

Press the new bearing on the shaft by 
pushing on the inner race only. 



120 PT 67 




********************* 



The outer bearing race may be removed 
and replaced as shown. 



120 PT 6 




The inner race is also replaceable, but 
must be pressed to the outside. 

There are shims under this bearing race 
which are used to set the ring gear and 
pinion tooth engagement. 



120 PT 69 




*******************^^^ 



- 46 - 



SECTION 50 
POWER TRAIN 
28 



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ASSEMBLING PINION AND DIFFERENTIAL GROUP 

There are two adjustments which must be 
made when reassembling the axle. Ring 
gear and pinion tooth pattern (1) and 
backlash (2) . 

The ring gear and pinion tooth pattern 
must be set before checking the backlash. 
The ring gear and pinion tooth pattern 
can be changed by adding or removing 
shims located under the inner bearing 
race. More shims will increase tooth 
engagement and less shims will decrease 
tooth engagement. 

If when servicing the axle, the old 
housing is to be reused, use the same 
shims under the bearing race. 

If a new housing is to be used or for 
some other reason it is not possible to 
reuse the old shims, determine the shim 
pack by measuring as shown. 

Using a press, install the bearing cup 
in the housing without any shims. Place 
the pinion assembly into the cup. 

Use the special tool JDST-10 as shown 
with a feeler gauge to determine the shim 
pack required. The thickness of the feeler 
gauge will determine the shim pack to be 
installed under the bearing cup. 

Remove the bearing cup, install the shims 
and replace bearing cup. 




********************* 



- hi - 



Install the pinion and spur gear in the 
housing as shown. Install the spacer 
with the flange over the splines. (Down) 
The spur gear is interchangeable. 



120 PT 71 



SECTION 50 
POWER TRAIN 
29 




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Press the outer bearing into position. 
Support the pinion shaft which the 
bearing is being pressed on. Press on 
the inner race only until the cup and 
cone are seated. 

Rotate the head of the pinion. There 
should be a slight amount of drag on the 
pinion. If it is too tight, tap on the 
outer end of the pinion shaft. 

Install the spacer washer and snap ring 
on the end of the pinion shaft. Spacers 
of various thicknesses are available if 
the original does not fit. 



120 PT 72 




******************:^** 



Install the cups on the bearings and 
place the differential assembly in the 
bearing cradles. The differential should 
fit snuggly in the cradles. Use a rubber 
mallet to seat the differential assembly 
in the cradles. If the fit is too tight, 
it may be necessary to remove some shims 
under the case bearings. 

Be sure teeth on ring gear and pinion 
are aligned when seating the differential 
in the cradles. The long side of the 
differential case points to the side 
cover plate. 

Install the bearing caps according to 
match marks and torque the bolts 30-45 
ft. lbs. 



120 PT 73 




********************* 



- 48 - 



SECTION 50 
POWER TRAIN 
30 



Paint the teeth of the ring gear with 
marking compound and turn the differen- 
tial a few seconds. 

Check the pattern of ring gear and pin- 
ion mesh. If a toe picture is present, 
move the pinion out. If a heel condi- 
tion is present, move the pinion in. 

Shown is a sample of various types of 
wear patterns . 

Note the portion of the ring gear called 
the toe and heel. Also note the side of 
the tooth called the drive side and 
coast side. The most accurate ring gear 
pattern will be seen on the drive side. 

Desirable Pattern: 

Note the wear pattern in the center of 
the tooth. This is the preferred pattern. 

Toe Pattern: 

This could result in a noisy gear set. 
Move the pinion gear away (out) from the 
ring gear. 

Heel Pattern: 

This could result in a noisy gear set 
and possibly early failure. Move the 
pinion toward (in) the ring gear. 

High Pattern: 

Move the ring gear toward the pinion 
to change this condition. (Backlash 
Ad jus tment) 

Low Pattern: 

Move the ring gear away from the pinion 
to change this condition. (Backlash Ad- 
justment) 



120 PT 74 






LOW FATTE»N 



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- 49 - 



Check the backlash with a dial indicator 
as shown. Backlash range is .003 to 
.007. If the backlash is not in this 
range, shims must be moved from side to 
side on the differential case bearings. 
If backlash is too tight, move ring gear 
away from the pinion. If it is too loose, 
move the ring gear toward the pinion. 



SECTION 50 
POWER TRAIN 
31 





120 PT 


75 






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********************* 



Install a new welch plug with the lip 
pointing in. Be sure the plug is straight 
when installing. Install the side cover 
and gasket. Be careful not to over 
tighten these side cover screws. 

Bolt the rear housing on the front hous- 
ing and torque the bolts 18-23 ft. lbs. 

Replace axle shafts and seals (15-30 ft. 
lbs.) and hubs (30-40 ft. lbs.) as ex- 
plained before. 

Reassemble differential assembly in the 
reverse procedure from installation. 



120 PT 52 




************* 



******* 



^^ 



- 50 - 



SECTION 60 
HYDRUALIC 1 



The hydraulics on the 120 are quite simi- 
lar to the 140 HI Tractor. 

All items concerning external hydraulics 
are covered in the 120 and 140 Service 
Manuals . 



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SECTION 70 
MISCELLANEOUS 1 



The miscellaneous items, such as steering, 
front axles, tie rods and spindles are 
covered in the 120 and 140 Service Manuals 
quite well. No further discussion will be 
made in this slide text. 



51 -